On an aircraft, engines such as auxiliary power units (APUs) require substantial mounting systems to withstand crash loads. The mounting systems must also provide certain degrees of freedom to ensure that the mounts do not fight or restrict one another. To meet these requirements, conventional mount systems simply provide adjustment through the use of shims. The mount systems and engines are typically machined/manufactured to very tight tolerances, such that the use of the shims provides for very limited adjustment.
When designing an aircraft, such as a first build of an aircraft, many variables may either be unknown or values for the variables may be incorrect or improperly assumed. For example, flight load induced deflections experienced by different portions of the aircraft may have an impact on various aircraft interfaces. A lack of flexibility across or between the interfaces can lead to expensive redesign efforts and delay. Furthermore, if the aircraft design is associated with multiple variants, flexibility or an adjustment capability may be needed to satisfy all interface requirements across all the variants.